1. Field of the Invention
The invention relates to an inductive sensor unit which is suitable in particular for detecting the position of a vehicle seat or for a gate shifting unit of an automatic transmission.
2. Description of Related Art
One such sensor unit, which is the point of departure for the invention and is defined by the preamble to claims 1, 13 and 16, is known from published international patent disclosure WO 2004/027994 A1.
From this prior art, it is also known that the travel measurement signals are spacing-dependent; that is, if the actuation element is guided along a curved path, or if the printed circuit board is not level, then changes in spacing enter into the measurement signals. The printed circuit board may be curved in a predetermined way, or a large, level printed circuit board may have unintentional curvatures. In the prior art, the spacing dependency is compensated for in the electrical evaluation circuit by means of standardization and calibration. Detecting the position of the electrical actuation element along the path that leads via the plurality of sensor coils is realized such that the changes in inductance of respective adjacent sensor coils are
From the published U.S. patent application U.S. 2003/0169033 A1, a sensor array for contactless position measurement is also known. This sensor array is used to determine the travel position of a vehicle seat. Each sensor element generates an output signal which correlates with one position from the set of possible seat positions. For the sensors, the Hall effect is utilized. For controlling the Hall sensors, either a magnet is provided which is moved past the sensors, or a magnetic shielding element is provided which is guided by a magnetic field that acts upon the sensors. Here again, the signal evaluation enables only limited position resolution based on the grid pattern of adjacent sensor coils.
From the prior art defined by German Patent DE 103 19 720 B3, a gate shifting unit for generating gear shifting signals for an automatic transmission of a motor vehicle is known. In this gate shifting unit, a shifting shaft with a selector lever is supported in a shifting block. The selector lever can be pivoted in a first plane S, but also perpendicular to it in a second plane T. To that end, it is pivotably connected to the shifting shaft. The motion of the selector lever often corresponds to the positions P, R, N and D, for the parking, reverse, neutral, and drive positions of the selector lever. The selector lever pivots a rotor with a shift finger that is accommodated in a modular housing. The shift finger pivots over a printed circuit board with an inductive sensor unit and represents an exemplary embodiment in which the shifting finger can carry the forklike actuation element of the present invention. Other spatial relationships and other paths of the conductive actuation element relative to the printed circuit board are also possible.